Iceland's Meteorological Office says two earthquakes early Monday rocked the caldera of Katla, one of the country's largest volcanos.

Gunnar Gudmundsson, a geophysicist, said authorities are monitoring the situation at the volcano in southern Iceland and described it as "a little bit unusual." The quakes measured magnitude 4.2 and magnitude 4.5 and were followed by some 20 aftershocks.

"People have been waiting for an eruption for 50 years," Gudmundsson said of Katla. "But there is no sign of an eruption."

Katla, named after an evil troll, is in southern Iceland about 140 kilometers (87 miles) from the capital, Reykjavik.

Iceland, an island nation in the remote North Atlantic, is a volcanic hotspot often hit by seismic activity. Its volcanos attracted international attention in April 2010, when ash from an eruption of its Eyjafjallajokull volcano grounded flights across Europe for days, disrupting travel for millions.

In the past, Katla has erupted in tandem with Eyjafjallajokull. Katla's last major eruption took place in 1918, and another has been expected since the 1960s.